1. Field of the Invention
The present invention relates to a case for enclosing articles with an RFID tag and an RFID system using the case, and more specifically, the present relates to a high-safety case and an RFID system in which information of the articles in the case can be read from or written to the RFID tags attached to the articles.
2. Related Art
Methods for reading and writing from/to a radio frequency identification tag (an RFID tag) include inductive coupling and electromagnetic coupling, which use electromagnetic induction by a magnetic field and radio waves of antennas, respectively. Both methods employ non-contact communication with an RFID reader/writer (or an IC tag scanner).
An RFID tag includes an antenna and an IC chip. When the antenna receives electric power and a signal from the RFID reader/writer, the controller of the IC chip accumulates the received electric power in a capacitor, and sends information stored in the storage section of the IC chip again from the antenna to the RFID reader/writer using the electric power.
Electromagnetic waves propagate with alternating electric and magnetic fields at a phase of 90 degrees. To this extent, when alternating magnetic flux due to magnetic change crosses a conductor including metal such as iron, aluminum, or copper, an eddy current is induced in the conductor, which generates magnetic flux in a direction that cancels the alternating magnetic field. Thus, such RFID tags, when metal is present in the front, back, or periphery, have the problem that information from the RFID tags cannot be correctly read because magnetic fields and radio waves are reflected or absorbed by the metal. Therefore, no metallic material is generally disposed between RFID tags and reader/writers.
To protect articles with RFID tags from external stress or shock during storage, transportation, or usage, one or a plurality of articles are often covered with a case. In this case, to carry out a communication between an RFID reader/writer and an RFID tag from the exterior of the case, metal cannot be used as the material of the case because it is an obstacle to communication. Therefore, articles with RFID tags are housed in cases made of a nonconductive material such as plastic.
Furthermore, when important information such as magnetic tape is housed in a package that carries an IC tag and is managed by an RFID system, a solid case made of metal such as duralumin is generally used to transport magnetic tapes in one go. In this case, no electromagnetic waves pass through the case because it is made of metal. Accordingly, to read the information from the IC tags attached to the articles in the case or to write new information thereto, the user must open the case to read the information with an RFID reader/writer.
Japanese Unexamined Patent Application Publication No. 2000-137873 discloses a system in which the entire RFID system, including articles with ID tags, an RFID reader/writer, a transmitting-receiving antenna, and a power circuit, is housed in a metal case, and in which ID information is read by a reader in the metal case without opening the cover of the metal case, and thereafter, the information is transmitted to another device via an external connector connected to a connector on the outer surface of the metal case. The communication using radio frequency (RF) by the RFID system is completely closed in the metal case. This is not suitable for transportation because of the heavy metal case including the reader, the power supply unit and other components.
Japanese Unexamined Patent Application Publication No. 2001-26308 discloses a system in which transmitting antennas and receiving antennas (coils) are disposed on the sides (six faces) of a returnable box, and when the returnable box passes by a sensor box (which also has transmitting antennas and receiving antennas), each face is made valid in sequence so that information of the ID tags in the returnable box can be read. This arrangement allows information to be sensed irrespective of the arrangement of the articles with ID tags in the box, that is, this arrangement prevents the directional characteristics of the ID tags. However, this arrangement needs to provide antennas on all the sides of the returnable box and requires such a complicated operation as to switch the antennas and as such, the returnable box would become complicated in structure, and have an increased weight.
When managing valuables such as magnetic storage media (e.g., tape, disks, etc.) containing customer information, noble metals, jewels, etc., using an RFID system, solid metal cases made of duralumin or the like are generally used for transportation. In this case, to read identification information (ID) of RFID tags, it is necessary to open every case and bring an RFID reader/writer to articles, resulting in low work efficiency. Moreover, for security or safe management, it would be an important challenge to read the information of ID tags attached to valuables without opening the metal transportation case.